1. Field of the Invention
The invention relates in general to a frame drawing method, a frame updating method and an associated mobile electronic device, and more particularly, to a frame drawing method and a frame updating method that update an image of a predetermined region in a user interface by a graphics component or display the image of the predetermined region through fetching a temporarily stored image, and a mobile electronic device applying the frame drawing method or the frame updating method.
2. Description of the Related Art
When operating a user interface displayed on a touch screen of a common mobile electronic device, a user may browse various kinds of information accessed by the user interface by finger sliding movements on the user interface. When an operation of the finger sliding movement corresponds to a maximum display range of a single page displayed on the user interface, a processor of the mobile electronic device employs a graphics component (usually implemented by software) to redraw an image displayed by the user interface. However, contents of the user interface processed by the graphics component are unaffected by the above sliding movement.
To reduce the load of the processor that utilizes the graphics component to redraw the image displayed by the user interface, a common mobile electronic device temporarily stores the image of the entire user interface (greater than the actual image of a single page of the user interface) as an additional snapshot. Thus, when the user operates the user interface by a sliding movement, the processor only needs to directly fetch the part to be displayed from the above temporarily stored snapshot to complete the display corresponding to the above sliding movement. Large amounts of processing time and computation that the graphics component requires for redrawing the entire user interface can then be saved, yielding better performance of a smooth sliding operation on the user interface.
However, as the size of the user interface expands, the range of the temporarily stored image of the user interface also becomes larger. As a result, by directly implementing the above method, certain mobile electronic devices equipped with a smaller memory may fail to present expected smoothness for the corresponding sliding movement on the user interface.
FIG. 1 shows a schematic diagram of an image distribution on a user interface displayed by a touch screen of a common conventional mobile electronic device. As shown in FIG. 1, a maximum drawing range supported by the touch screen is T1, whose size is restricted by hardware specifications of the mobile electronic device. A drawing region T2 is a fixed viewable range of the user interface displayed by the touch screen. From perspectives of a user, the drawing region T2 does not exceed beyond the drawing region T1 regardless of how the drawing region T2 is moved by a touch command. In other words, with respect to processes of the mobile electronic device, the drawing region T2 is moved according to a coordinate system established by the drawing region T1.
When a user of the mobile electronic device sends out a user command by a sliding movement to slide the user interface upward by a distance D, a result that the user observes is in equivalence sliding the drawing region T2 by the distance D. However, from perspectives of the mobile electronic device, the drawing region T2 is substantially unmoved, and the drawing region T1 is in fact slid upward by the distance D. On the other hand, for the coordinate system established based on the drawing region T1, a relative position of the drawing region T2 is moved downward by the distance D.
As previously stated, with an increasing range of the drawing region T2, the amount of computation brought upon the mobile electronic device by a movement of the drawing region T2 also increases, thus obstructing the touch screen from presenting a smooth sliding effect.
FIG. 2 shows a schematic diagram of an image distribution on a user interface displayed by a touch panel of another common conventional mobile electronic device. As shown in FIG. 2, images on the touch panel are applied with a concept of hierarchical control. Assuming that the range of a drawing region A1 is a maximum controllable range of the touch screen, a drawing region A2 covering a part of the drawing region A1 may be regarded as a sub drawing region of the drawing region A1, and a graphics component for displaying the drawing region A1 may be utilized to control a graphics component for displaying the drawing region A2. Similarly, the graphics component for displaying the drawing region A2 may be utilized to control a graphics component for displaying a drawing region A3.
Under the mechanism shown in FIG. 2, when a user command sent by a user is for sliding the drawing region A3, it is known from the hierarchical relationship of the drawing regions A1, A2 and A3 that, all of the drawing regions A1, A2 and A3 need to be redrawn in response to the user command. However, if the user command is for sliding a part that is in the drawing region A2 but excluding the drawing region A3, the drawing region A3 that is not operated by the user command also needs to be redrawn as the drawing region A2 needs to be redrawn. Under the abovementioned circumstances of the increasing size of the user interface, the need of compulsorily redrawing a region such as the drawing region A3 that is not operated by a user command due to redrawing a parent drawing region is becoming frequent occurrences, thereby posing a significant load on the amount of graphics computation for a mobile electronic device.